1. Field of the Invention
The present invention relates generally to air pumps. More particularly, the present invention relates to an air pump which is operated by the drive chain of a bicycle.
2. Background Art
Air pumps have long been employed to inflate various articles, such as pneumatic tires, air mattresses, footballs and basketballs, inflatable toys, and the like. By their very nature, many of these articles need to be inflated in field environments, far from filling stations or other facilities having installed air compressors. Consequently, a great many types of portable air pumps have been used or proposed, with varying degrees of success.
Perhaps the best known example of a portable air pump is the hand-operated reciprocating type, which is frequently carried clipped to the frame tubes of a bicycle. These pumps typically have a single-acting piston and cylinder, the piston being operated by means of a long rod to which a handle is attached: the cylinder and handle are gripped in opposite hands and reciprocated back and forth to drive air out of the cylinder and into the article to be inflated. While these typical hand-operated reciprocating air pumps have the advantage of simplicity, they also exhibit a number of shortcomings. Firstly, they are fairly slow to operate, the speed of the reciprocating action being limited to that with which the operator can move his hands back and forth relative to one another. This disadvantage becomes quite burdensome when inflating relatively large articles which require significant volumes of air. Furthermore, inasmuch as the handle operates directly on the piston rod, these pumps provide no mechanical advantage to assist the operator; consequently, it can be very difficult to attain high air pressures (as required by many modern bicycle tires) using such pumps. Moreover, since such pumps typically employ pistons and cylinders having small diameters and very long strokes, they are ordinarily quite long and thus difficult to stow. The long cylinders and piston rods are also typically made of metal, rendering it difficult to make such pumps as light as may be desired.
The need for portable air pumps which are compact, light, and fast acting has become more pronounced in recent years, particularly with the advent of very lightweight bicycles. For example, speed of operation and minimum weight can be crucial factors in various competitive events, such as triathalons, which involve the use of bicycles.
A number of attempts have been made to employ the drive system or motion of the bicycle itself to operate an air pump. For the most part, these pumps have been mounted to turn with the wheel of the vehicle so as to inflate the tire while the vehicle is in motion. For example, U.S. Pat. No. 1,169,705 to Wilkes (1916) shows a pumping apparatus having a pump cylinder, with a piston being positioned in the cylinder and having a piston rod. This assembly is mounted to the hub of the wheel (in this case, that of a motorcycle), and rotates therewith. There is a linkage having a roller which extends out through the spokes of the wheel so as to be activated by a track which is fixed to the frame of the vehicle, causing the piston rod and piston to reciprocate so as to pump air through a flexible hose into the tire on the wheel.
A variety of other air pumps have been proposed which, like that of Wilkes, are mounted to the hub of a wheel so as to rotate therewith and pump air to a tire on the wheel. For example, U.S. Pat. No. 797,447 to Merry (1905) shows a rotating, hub mounted piston assembly which engages a slanted disc on the frame of the bicycle so as to impart a reciprocating motion to the piston. U.S. Pat. No. 744,483 to Carlberg (1903) shows a pump assembly which rotates with the wheel and which has a lever which extends from the wheel and cooperates with a fixed cam plate on the bicycle frame so as to reciprocate the cylinder along a wire guide which is fixed to the wheel rim. U.S. Pat. No. 652,997 to Crandall (1900) shows a pump assembly which rotates with the wheel of a bicycle and which has a protruding cam follower which engages an eccentric cam mounted to the bicycle frame so as to impart a reciprocating motion to a piston in the pump cylinder. U.S. Pat. No. 624,417 to Wickersham et al. (1899), U.S. Pat. No. 596,223 to Wickersham et al. (1897), and U.S. Pat. No. 559,418 to Spencer (1896) show varieties of air pump arrangements having pinion gears which protrude from the rotating pump assemblies and engage larger stationary gears which are mounted to the vehicle frames; rotation of the pinion gears operates crank arms which in turn reciprocate pistons of the pumps.
A variety of other devices have been proposed which are driven by the chain and sprocket drive of a bicycle, or which otherwise utilize the rotational motion of bicycle components. For example, U.S. Pat. No. 681,565 to McCune (1901) shows a fan which is mounted adjacent to the handlebars of a bicycle, the blades of which are rotated by means of a belt drive from the crank assembly of the bicycle. U.S. Pat. No. 868,658 to Hamacher (1907) discloses a bicycle in which movement of the rider's feet apparently reciprocates pump cylinders to generate compressed air which acts against vanes of a drum to cause rotation of a shaft which is presumably attached to a drive for the back wheel. U.S. Pat. No. 3,283,997 to Bambenek et al. discloses a portable ventilator in which a stationary bicycle has a chain and sprocket drive which rotates a large pulley, which in turn drives a belt that provides power to the ventilating apparatus. U.S. Pat. No. 4,677,328 to Kumakura discloses a bicycle generator having a stator which is fixed to the bicycle frame and a rotor which rotates with the flange of the wheel.
It will be appreciated that each of the above-described bicycle-driven devices adds undesirable weight to the bicycle to which it is mounted. Furthermore, notably with respect to the air pumps, many of these devices are characterized by complicated, heavy, and inefficient mechanical linkages. The rotating pump assemblies would also have a deleterious effect on the balance of the wheels to which they are affixed. Furthermore, inasmuch as these devices operate while the vehicle is in motion, they would appear to be able to inflate only that tire which rotates on the wheel together with the pump: these devices are thus unsuitable for inflating the other tire of the bicycle, or for inflating articles which are separate from the bicycle, such as air mattresses, footballs, or the like.
A number of air pumps are known apart from those which are bicycle driven. Amongst these is that shown in U.S. Pat. No. 2,472,647 to Convins (1949), which discloses a double-acting reciprocating pump in which there are two pistons having an interconnecting element. The interconnecting element has a slot which extends at right angles to the direction of reciprocation of the pistons, and which is also at right angles to the axis of a crank. An end portion of the crank arm is received in the slot and as the crank arm rotates, the interconnected pistons are moved back and forth for the pumping action. There are inlet and outlet valves for each cylinder, the outlet valves being able to be connected to a common output line so as to obtain a more or less constant flow of air from the pump. Similar piston-cylinder arrangements are shown in U.S. Pat. No. 3,517,652 to Albertson (1970), which discloses a two-stroke engine, and U.S. Pat. No. 3,451,276 to Wadlow et al. (1969), which discloses an actuator mechanism. None of the devices described in this paragraph is adapted for use with a bicycle drive mechanism.
Accordingly, there is a need for a portable air pump for inflating bicycle tires and other articles, which is light in weight, and efficient and fast in operation. Furthermore, there is a need for such a device which provides a mechanical advantage so as to permit an operator to inflate articles to high pressures, as well as for such a device which is compact and readily stowable.